Judge Susan Nelson ruled in May that Bettman possessed “unique or special knowledge relevant” to the lawsuit and that the plaintiffs will have an opportunity to first depose other witnesses.

According to the report, Bettman is set to give his testimony at 10 a.m. ET in front of Nelson in New York City.

NHL deputy commissioner Bill Daly and director of hockey operations Colin Campbell will also be deposed and forced to answer questions relevant to the lawsuit. Philadelphia Flyers trainer Jim McCrossin and former Pittsburgh Penguins physician Charles Burke were also sent subpoenas and expected to testify.

More than 60 former NHL players, including lead plaintiffs Dan LaCouture, Michael Peluso, Gary Leeman, Bernie Nicholls, David Christian and Reed Larson, sued the league in November 2013 claiming they did not do enough to protect them from head injuries, failed to properly warn players of risks of brain trauma, and consistently promoted violent play.

“Plaintiffs relied on the NHL's silence to their detriment,“ the lawsuit said.

The players also said that the league had been blocking access to Bettman for his testimony in the case.

Bettman has said there is no evidence linking hockey and chronic traumatic encephalopathy or CTE, a degenerative disease caused by repeated brain trauma.

“From a medical science standpoint, there is no evidence yet that one necessarily leads to the other,” Bettman said. “I know there are a lot of theories, but if you ask people who study it, they tell you there is no statistical correlation that can definitively make that conclusion.”

The lawsuit came months after 4,500 former players reached a settlement with the National Football League over the same type of concussion-related complaints.